The Voice Coaches Open Up About Their Tight Bond — and Gwen Reveals Why She's Jealous of Adam (Hint: It Involves Blake Shelton)

“I remember when I saw him at the meeting at NBC, I was instantly very taken by him ’cause he was definitely not your typical country artist,” Levine told PEOPLE recently on set of NBC’s hit singing competition show. “He was not a cookie-cutter guy, and the second we met, we were friends. All of the bulls— that we do comes from a place of love.”

Alicia Keys — who’s back as a coach for her second season — was also pleasantly surprised by Shelton. “I like him so much,” says the singer. “I mean, I didn’t think I was gonna not like you, but I didn’t expect to like you. You’re a cool guy!”

The first time Shelton met Levine, “I didn’t know what the hell was going on,” says Shelton. “It was this skinny guy with a white T-shirt with the collar all stretched out. I remember turning to my manager and saying, ‘I think that’s Adam Levine.'”

Brian Bowen Smith/NBC

Now years later, the pair have seen each other through many of life’s milestones and found lasting friendship. “He’s one of the most loving people I’ve ever known,” says Shelton. “We drive each other nuts, but outside of this world, he’s one of my best friends and it’s because of his heart. He needs his face slapped around, but he has a huge, huge heart.”

“It’s so cool that we are really close. Blake and Alicia and Shakira and Usher and Pharrell. It’s like holy s—, I was able to make all these new friends I never would’ve made in a million years,” adds Levine. “We were brought together by this crazy show. I feel so lucky to have at least at the end of the day, beyond the show itself, to have made really good friends.”

For all the details about the new season of The Voice and more on the coaches’ close friendships, pick up the latest issue of PEOPLE, on newsstands Friday.

It’s no longer just a bromance now, though. After joining the show several seasons ago, Gwen Stefani and Shelton started dating more than a year ago and are stronger than ever.

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“I’ve had the longest love affair with Blake out of everyone,” says Levine about working through 12 seasons with Shelton.

“God, I wish I was you,” joked Stefani. “I made my best friend. I found my best friend!”

It’s all good, though — Levine’s more than willing to share his best pal. “The best friend a woman can have,” he teased Stefani.